1. Field of the Invention
The cryogenic thermal switch automatically varies the heat transfer path between two separate temperature environments. It is particularly useful in automatically thermally connecting the cold stage of a cryogenic refrigerator to its heat load upon cold production by the refrigerator.
2. Description of Related Art
Large conventional refrigeration systems often have a plurality of compressors arranged in parallel together with a plurality of expansion valves arranged in parallel. Each expansion valve expands the fluid into an evaporator which is thermally associated with its load. Quite often a common high-pressure refrigerant line is employed from the output of the plural compressors, together with a common compressor suction line. Compressors can be added to or removed from the active refrigerant flow path, as required.
However, in cryogenic refrigerators the compressor is closely positioned and thermally coupled to the heat load because the refrigerant fluid remains in the gaseous state and is expanded in the cold cylinder of the refrigerator. It is thus much more difficult to provide parallel refrigerant sources to one or more thermal loads. There is no known prior art which satisfies the requirement for a self-contained thermal switch which can supply high contact forces for good thermal conduction while conducting, and low heat leak in the non-conducting state, and which is fully contained to retain all the dynamic reaction forces within the switch envelope.